Drill bit assembly



Nov. 30, 1948. V w. E. CARR 2,454,771

DRILL BIT ASSEMBLY Filed May 8, 1944 2 Sheets-Sheet l FiG. Z

lNVENTOR WALTER E. CARR BY 1 l ATTORNEY W- E. CARR Nov. 30, 1948.

K i mv OR WALTER E. CARR BY mu ATrbRNEY Patented Nov. 30, 1948 2,454,771nnmr. arr ASSEMBLY Walter E. Carr, Spokane, Wash, assignor, by

decree of distribution,

Spokane, Wash.

to Sarah Jane Carr,

Application May 8, 1944, Serial No. 534,542

4 Claims. 1

The present invention relates to certain new and useful improvements ina drill bit assembly for detachable drill bits such as used in hard rockdrilling, in mining, quarrying, etc.

According to the present invention, the drill bit is detachably securedto the drill rod by means of cam faces on the interior of the drill bit,frictionally engaging with corresponding cam faces on the drill rod.These cam faces are tapered, but

the taper is used solely for the purpose of disengagement and does notexert any force in effecting engagement, which is solely by relativerotation of the cam faces. The skirt of the drill bit seats against acollar on the drill rod so as to pre clude the impact of the drillingoperation from driving the drill rod into tighter tapered engagementwith the drill bit. In this manner, the drill bit is engaged with thedrill rod, solely by the relative rotation of the cams, which is ofprime importance in providing for quick and easy removal of the drillbit when dulled by use.

For removing the drill bit from the drill rod, the invention provides adriving block which saddles over the drill rod and butts against thedrill bit at diametrically opposite sides, so that each blow of a hammercan be directed to both sides of the drill bit simultaneously, which isof paramount importance in removing the drill bit. This driving blockeliminates all need to hammer directly upon the drill bit, which is avery ineflicient mode of removal, and exceedingly diflicult toaccomplish by any attempt to hammer the bit in reverse rotation.

The drawings show the invention in the form in which it has been reducedto practice and thoroughly tested in various conditions oi hard rockdrilling. Fig. 1 shows a drill rod having an integral collar againstwhich the skirt of a bit is seated, and a driving block is shown (partlyin section) bu ting against the head of the drill bit. in position fordriving the bit off from the rod.

Fig. 2 is an enlarged sectional detail bit and rod of Fig. 1.

Fig. 3 and Fig. 4 each show a transverse section through Fig. 2 at theline X-X, Fig. 3 showing the cams in initial position, and Fig. 4showing of the drill .the cams frictionally engaged for securing thedrill bit upon the rod.

Fig. 5 is a diagrammatic showing of Fig. 3 for.

Fig. 8 is a transverse section of the driving block, taken along theline 88 in Fig. 7.

In carrying out the present invention the usual drilling rod R is hereshown as round but may be hexagonal or any other suitable shape, and isusually provided with an axial bore as indicated at K, the purpose ofwhich is exceedingly well known.

This drill rod R is expanded into an integral collar as indicated at Cand provided with a bit shank E of smaller size so that the collarprovides an annular shoulder 2.

This bit shank E is formed with cam sides 3 and 4 which are oppositelyeccentric to the axis of the bit shank E which of course is axiallyaligned with the drill rod R. The arrangement of these cams is best seenin the diagrammatic showing of Fig. 5 (see also Fig. 3) and as shown inFig. 2

these cams are tapered towards the end of the bit shank E.

The detachable drill bit B may have any suitable cutting head H as thepresent invention is not concerned with the kind of cutting facesemployed. As best seen in Fig. 2, the bit B has an annular skirt S whichis of the same size as the aforesaid collar 0, and as here shown, thecutting head H forms square shoulders T extending outwardly from theskirt S; however, it is conventional practice to flare the skirt insteadof employing square shoulders and it will be understood that either modemay be employed in the present invention.

. The interior of this skirt S is provided with cams I and 6 which matewith the aforesaid cams 3 and 4, and are correspondingly tapered as willbe seen from Fig. 2, the relative arrangement of the cams being bestseen in the diagrammatic showing of Fig. 5 (see also Fig. 3)

In Fig. 3 and Fig. 5 these cams are shown in their initial position, andit will be seen that there is reasonable clearance between the sams onthe skirt S and those on the bit shank E, so that the drill bit can bemanually placed in position on the bit shank and then manually rotatedto the position shown in Fig. 4 so that the cam surfaces will engageover considerable area and hold the drill bit upon the drill rod. Infact, a minor twist with the hand will afford suiliciently tightengagement to enable the drill rod to be lifted by grasping the bit.When the bit contacts the work in actual drilling, the constant rotationof the drill rod will urge the cam faces into exceedingly tightengagement and securely hold the bit upon the rod with assurance thatthe bit will not be lost in the bore hole.

As shown in Fig. 2, the bit shank E is of the same length as the depthof the interior of the skirt S, so that the bit seats on the end of theshank E, and also, the skirt S seats on the collar C, so that it isimpossible for the impact of the drilling operation to urge the bitshank any deeper into the drill bit, which would drive the cams intoo'bjectionably tight tapered engagement and also be likely to split theskirt and also split the head of the drill bit, as sometimes occurs inthe prior art. Also, this seating of the drill bit, both internally andexternally, is of considerable advantage in. keeping out refuse whichwould otherwise be forced inside the skirt and cause difllculties, assometimes occurs with threaded bits, when a workman carelessly fails tofully screw the bit on before starting to drill. With the presentinvention, the loose fit of the bit in the initial position assures thatthe skirt S will seat on the, collar C without any effort on the part ofthe work'- men; and since the bit seats both internally and externallyupon the drill rod, it affords about twice as much area for the impactof the drilling operation and therefore enhances the drilling eificiencyof the bit, and also eliminates the well known fault of objectionablydriving the rod into the drill bit and the disadvantages resultingtherefrom. When the drill bit seats only on the end of the rod, thegreatest wear occurs in the center of the bit, and when the bit seatsonly on the skirt, the greatest wear occurs on the outer portions of thebit, and the center of the bit gradually caves in by the impact ofdrilling. The double seating on the skirt and also on. the end of thebit shank as afforded by the present invention, assures uniform wearover the entire cutting surface of the bit, and thus prolongs the usefullife of the bit and enables it to be sharpened a greater number oftimes.

For removing the drill bit from the rod, I provide a driving block suchas shown at D in Fig. 1 or at D in Fig. 6, Fig. 7 and .Fig. 8.

As shown in Fig. 6 this driving block D has a body portion l I which ischannelled on its underside as best seen at l2 in Fig. 8 where thischannel is shown as of inverted U-shape so as to saddle over a round rodor else a hexagonal rodor octagonal rod of the same size. This channelextends full length of the block and is enlarged at l4 so as to clearthe collar and the skirt S of the bit B, and thereby enable the forwardend IE to butt against the shoulders T on diametrically opposite sidesof the drill bit. This driving block is freely slidable upon the drillrod so that it can readily be moved into contact with the drill bit.

This driving block is thick walled to give suitable mass and weight, andits rear end is provided with a thickened head H to add further mass andweight, and also to provide for suitable impact with a hammer, by meansof which the drill bit can be quickly and easily removed by a few blows.

In some instances, the drill bit canbe removed by the driving blockalone, without resorting to the use of a hammer. That is to say that thedriving block can be slidably moved along the drill rod in a few quickblows against the drill bit, and by reason of the fact that the drivingblockcon.- tacts the drill bit at diametrically opposite sides, removalcan be accomplished with less force than would otherwise be required bypounding with a hammer directly on the bit. Due to the fact that thisdriving block saddles over the rod. it is effectualiy guided to squarelycontact the bit at each blow. -The body'portion H affords a convenienthand grasp for the workman in slidably moving the driving block upon therod at each pounding stroke; and to afford a more secure hand grasp itis advisable to provide a flange as shown at [6.

In instances where a hammer is not employed, the thickened head I!affords weight and mass to enhance the manual pounding with the drivingblock itself, and where greater force is required this head I! affords aconvenient and efficient face for impact with a hammer.

As shown in Fig. 1 the driving block may be provided with a handle suchas l8 instead of the aforesaid head l1, and in this instance the workmanuses the handle l8 to hold the driving block in position against thedrill bit while the end I9 is pounded with a hammer to drive the drillbit ff the rod in the same manner as previously described, this drivingblock D being otherwise essentially the same as already described andhaving the aforesaid inverted U-shaped channel so as to saddle over thedrill rod.

Either of these driving blocks can also be used on bits having a flaredskirt instead of the illustrated square shoulder.

It will be noted that the driving block confines the force of thehammering, solely to endwise movement, of the drill bit, so as todislodge the tapered surfaces of the rotary engaged cams. Thus thedriving block precludes any attempt to rotate the cam engagement byhammering, which is a far more diflicult mode of removal than endwisedriving. Moreover the driving block affords endwise driving on bothsides of the bit simultaneously, and. greatly enhances the efliciency ofremoval, thus saving much time and effort, which can otherwise be spentin actual drilling. No matter whether the driving is by pounding withthe driving block itself or by hammering upon the driving block, thesaddle arrangement upon the rod precludes any glancing blows upon thebit which would be likely to break off corners of the bit and endangerthe workman by flying pieces of metal.

It will be seen that the present invention effectually solves theproblem with which the prior art was concerned but failed to solve inlike manner. It will also be seen that the disclosed structure unitesthe various forces so that they function in proper relation to eachother without setting up contraindicated forces objectionably affectingeach other. The problem has long been of considerable consequence to theindustry, and the present invention meets the existing need and want,with better success and satisfaction than has heretofore been obtained.

,As here shown, the cams 3 and 4 constitute a pair of identical cams,each offset from the axis of the drill rod an equal amount and inopposite directions along the same diameter. In like manner the cams 5and 6 constitute a pairof identical cams, slightly larger and matingwith the paired cams 3 and 4. This aflfords a quicker take-up of theclearance between the paired cams 5 and 6 on the skirt S and the pairedcams 3 and 4 on the bit shank E, than would otherwise be accomplished byemploying one continuous cam instead of the paired cams 3 and 4, and acorresponding continuous cam instead of the paired cams 5 and 6. Thepairedcams as herein discosed, greatly lessen the rotation required totake-up a given amount of clearance; and furthermore, the non-contactingportions of the tightly engaged cams, isdivided equally at diametricallyopposite positions so as to equalize the stresses, in contradistinctionto the aforesaid continuous cams which would of necessity result in thenon-contacting portions being all on one side and setting up lateralstresses in the opposite direction and against the areas having theleast contact.

The paired cam structure herein disclosed, eliminates the need ofconfining the clearance so closely as is required. by continuous cams,and thus the paired cams afford greater latitude of tolerance and aremore economically practical to manufacture in large scale production.which is of course required for a device of this kind.

Furthermore, if continuous cams were used, their rotary engagement wouldbe much more gradual, and the rotation of the drilling operation wouldconsequently urge them into tighter frictional engagement than isnecessary for the purpose. Thus the paired cams of the presentinvention, eliminate the inherent inaptitudes of continuous cams, andrender it much easier to remove the drill bit, because the paired camsdo not engage so exceedin ly tight as is needlessly the case withcontinuous cams. These paired cams engage sufilciently tight to securelyhold the drill bit upon the rod, but are more easy to remove, than ifcontinuous cams were employed; thus the paired cams save the time andeffort of the workman and enable him to work with better efliciency.

I claim as my invention:

1. A drill bit assembly comprising a drill rod including a tapered bitshank having a pair of external cam faces thereon and eccentric to eachother, a drill bit including an annular skirt having a pair of internalcam faces mating with said external cam faces and tapered to correspondtherewith, said drill rod having an integral collar against which saidskirt seats, said bit shank being the same length as the interior lengthof said skirt so as toseat therein when said skirt also seats on saidcollar, whereby the seating of said skirt indexes the maximum taperedengagement of said cam faces and whereby the internal and externalseating of said bit excludes refuse from entering between said camfaces, the cam faces on said skirt having sufficient clearance from thecam faces on said bit shank to afford a loose fit in the initialposition and to afford a tight frictional engagement when rotated afraction of a turn.

2. A drill bit assembly comprising a drill rod including a tapered bitshank having a pair of external cam faces thereon and eccentric to eachother, a drill bit including an annular skirt having a pair of internalcam faces mating with said external cam faces and tapered to correspondtherewith, said drill rod having an integral collar against which. saidskirt seats to thereby index the maximum tapered engagement of said camfaces and thereby preclude longitudinal driving of said tapers againsteach other, the cam faces of said skirt having suflicient clearance fromthe cam faces on said bit shank to afford a loose fit 6 in the initialposition and to afford a tight frictional engagement when rotated afraction of a turn.

3. A drill bit assembly comprising a drill rod inciuding a bit shank.having curved cam sides tapered towards thev axis of said rod, a drillbit including an annular skirt having internal cam sides mating withthe. cam sides on said bit shank.

and tapered to correspond therewith, said drill rod having an: integralcollar against which said:

tapered engagement of said cam sides and whereby the internal andexternal seating of said bit excludes refuse from entering between saidcam sides, the cam sides onv said skirt having sufllclent clearance fromthe cam sides on said bit shank to afford a loose fit in the initialposition and to afford a tight frictional engagement when rotated afraction of a turn.

'4. A drill bit assembly comprising a drill rod including a bit shankhaving curved cam sides tapered towards the axis of said rod, a drillbit including an annular skirt having internal cam sides mating with thecam sides on said bit shank and tapered to correspond t erewith, saiddrill rod having an integral collar against which said skirtseats tothereby index the maximum tapered engagement of said cam sides andthereby prc elude longitudinal driving of said tapers against eachother, the cam sides on said skirt having sufiicient clearance from thecam sides on said bit shank to afford a loose fit in the initialposition and to afford a tight frictional engagement when rotated afraction of a turn, said drill bit having a cutting head larger thansaid skirt, and square shoulders formed at the rear of said cutting headto engage a tool for longitudinally driving said bit off fromsaid shank.

WALTER E. CARR.

REFERENCES CITED The following references are of record in the tile ofthis patent:

UNITED STATES PATENTS Number Name Date 803,911 Leyner Nov. 7, 19051,360,897 Dailey Nov. 30, 1920 2,234,486 Craig Mar. 11, 1941 2,307,507Hutton Jan. 5, 1943 2,312,471 Low Mar. 2, 1943 FOREIGN PATENTS NumberCountry Date 7 110,872 Australia June 19, 1940 1,806 Great Britain Apr.29, 1.876

